This is an odd one.
I was typing on an apple "smart keyboard" connected to an iPad Pro. "Notes" REALLY wants to capitalize the first letter of each line, and "Mail" REALLY wants to capitalize any letter after you type a ":" character.

When I'm using the on-screen keyboard it is easy to see that the 'Shift' button is engaged, and press it to disengage it. However, for the life of me, I could not get the shift to disengage while I had the apple keyboard attached to the iPad Pro! I had to physically disconnect it in order to bring up the on-screen keyboard where I could then disengage the 'Shift' button.

Does anyone know a way to do this without disconnecting the physical keyboard?

I have auto-caps turned off in settings on my iPad Pro and iOS still has errant auto-capitalization issues.

It seems to be linked to how the OS interacts with various apps.

For example, in Word for iOS, the app will spontaneosly capitalize the letter "i" if it's at the beginning of a word. (but not at other times)
To get rid of this, I have to back space, hold down the shift key, and type "i" again, and it types a lowercase "i".